For example a 2.54mm (0.1") Pitch IDC Socket uses 1.27mm (0.05") Ribbon cable.
But worry no more here is my simple guide to getting the right combination of cable and connectors across the most common ranges:
Connector Pitch: Cable Pitch:
1.27mm (0.05") 0.635mm (0.025")
2mm (0.79) 1.mm (0.039")
2.54mm (0.1") 1.27mm (0.05")
Many people get confused because some cable manufactures list their dimensions in inches and connectors in millimetres, and vice versa.
I hope this has been helpful and will aid you in choosing the right combination of cable & connectors.